The present invention relates to medical imaging, and in particular to systems that set one or more image processing parameters.
In ultrasound medical imaging, various imaging parameters are set for acquiring and processing image data. For example, relative delays and apodization for transmit and receive beamforming, depth dependent and overall gains, an amount of persistence or other filtering, weightings, types of filters, spatially compounding variables, dynamic range or other image processing parameters are set. For example, a B-mode signal is adjusted for gain and dynamic range before being mapped to a range of gray levels or colors for display. The dynamic range can conveniently be set by the user by means of a display dynamic range control that is independent of range in azimuth position in the image. The gain can be varied by the user using a depth or time gain compensation control along with a master gain or B-mode gain control. The depth or time gain control may vary in range (axial dimension) while a master gain is independent of both range and lateral (azimuthal) position. As another example, a focal point or depth of imaging is selected for determining beamforming parameters. As yet another example, a type of imaging is selected that uses spatial and/or persistence compounding.
In addition or as an alternative to user selection of the various imaging parameters or user selection of a setup associated with groups of imaging parameters, the imaging parameters may be set adaptively as a function of ultrasound data. For example, U.S. Pat. No. 6,398,733, the disclosure of which is incorporated herein by reference, discloses adaptively determining one or more of gain, dynamic range and post-processing maps in response to ultrasound data. Amplitudes associated with soft tissue are determined and a gain or dynamic range is set in response to the amplitudes. Ultrasound data acquired without transmission of energy or selected as representing noise is used to adaptively determine gain or dynamic range.
The other imaging processing parameters discussed above may also be adaptively varied. For example, focusing delays or apodization values are adaptively determined as a function of ultrasound data to provide for aberration correction. As another example, a filtering parameter, such as a persistence or spatial compounding parameter, is adaptively varied as a function of ultrasound data, such as to avoid blurring. However, random or statistical fluctuations in the data may cause undesired optimization, resulting in flickering through an entire image or within local regions of an image.
To avoid undesired automatic optimization, the adaptive optimization is only initiated in response to a user input. For example, the user selects an automatic gain function, and the system adaptively determines a gain at that given instance in time for application to subsequent data until the user reselects the automatic gain optimization. As another example, the user changes one imaging processing parameter, and the system then automatically optimizes other imaging parameters. However, manually initiating adaptive optimization of imaging parameters slows down work flow. The user is required to make quick and accurate judgments during real time imaging as to when to apply the optimization, often resulting in images not being optimal.
U.S. Pat. No. 6,579,238 (U.S. application Ser. No. 09/791,405, filed Feb. 23, 2001), the disclosure of which is incorporated herein by reference, discloses initiating the adaptive adjustment of gain or dynamic range automatically at intervals. However, initiation of adaptive optimization of imaging parameters at regular intervals may be distracting or annoying to the user. Depending on how often the optimization is applied, a frame rate reduction or unacceptable delays between optimizations may result. Detecting large changes in the input signal, such as a large change in the sum of input signals for a frame of data or a region of a frame of data, is also disclosed for initiating adaptive optimization. Detection of large motion signals based on frame correlation may also be used to initiate adaptive adjustment of gain or dynamic range. Initiating adaptive optimization of imaging parameters based on large changes or motion detection may be susceptible to noise, flash artifact, changes in the anatomy or region of the anatomy being imaged. With too sensitive of detection of change or motion, change due to heart motion may automatically initiate adaptation, resulting in variance between images due to imaging parameters rather than anatomy differences.
In video cameras, motion due to object motion as opposed to panning and shaking of the video camera may be separately identified for different processing of the video information. For example, see U.S. Pat. No. 5,767,922 Zabih, et al “Apparatus and process for detecting scene breaks in a sequence of video frames”, U.S. Pat. No. 5,835,163 Liou, et al “Apparatus for detecting a cut in video”, and U.S. Pat. No. 5,844,613 Chadda, “Global motion estimator for motion video signal encoding”. These patents attempt to separate frame changes due camera panning, motion of objects in the scene and changes due to different video segments filmed at different times. The techniques are computationally very demanding.